Correction of Residual Hyperopia After Cataract Surgery ... - Iogen

Correction of Residual Hyperopia After Cataract Surgery
Using the Light Adjustable Intraocular Lens Technology
ARTURO CHAYET, CHRISTIAN A. SANDSTEDT, SHIAO H. CHANG, PAUL RHEE, BARBARA TSUCHIYAMA,
AND DANIEL SCHWARTZ
● PURPOSE: To determine whether residual hyperopia
could be corrected postoperatively using the light adjustable
lens technology in patients undergoing cataract
surgery and light adjustable lens implantation.
● DESIGN: Prospective, nonrandomized clinical trial.
● METHODS: Fourteen eyes of 14 patients were studied. The
manifest refraction, uncorrected visual acuity (UCVA), and
best-corrected visual acuity (BCVA) were determined with
follow-up time to determine the achieved refractive corrections
and their stability.
● RESULTS: Of 14 eyes, 13 eyes (92.9%) achieved
0.25 diopters (D) of the target refraction at one day post
lock-in, with 100% of the eyes achieving the targeted
refractive adjustment within 0.5 D or better up to six
months postoperative follow-up. All eyes treated show no
change in manifest spherical refraction >0.25 D between
one day post lock-in, and three and six months postoperative
visits. The data demonstrate the stability of the
achieved refractive change after the adjustment and
lock-in procedures. The mean rate of change was 0.006
D per month, which is six times more stable than that of
refractive procedures.
● CONCLUSIONS: Residual hyperopia errors in the range of
0.25 to 2.0 D were successfully corrected with precision
and significant improvement in UCVA and without
compromising BCVA using the light adjustable intraocular
lens technology. (Am J Ophthalmol 2009;147:392–397.
© 2009 by Elsevier Inc. All rights reserved.)
HYPEROPIA IS ONE OF THE LEAST DESIRABLE REfractive
outcomes after cataract surgery. While
careful preoperative biometry and intentional
targeting for a small amount of residual myopia can
prevent most hyperopic surprises, residual hyperopia has
been more difficult to eliminate in refractive surgery
patients who subsequently develop cataracts. Attributable
to corneal changes following laser in situ keratomileusis
(LASIK) or photorefractive keratectomy (PRK), corneal
power is often overestimated, and these patients are
frequently left hyperopic after cataract surgery. 1–13 A broad
Accepted for publication Aug 26, 2008.
From the Codet Vision Institute (A.C.), Tijuana, Mexico, Calhoun
Vision Inc (C.A.S., S.H.C., P.R., B.T.), Pasadena, California, and the
Department of Ophthalmology, University of California at San Francisco
(D.S.), San Francisco, California.
Inquiries to Arturo Chayet, Ave. Padre Kino No. 10159, Tijuana,
Mexico 22320; e-mail: arturo.chayet@codetvision.com
array of intraocular lens (IOL) power calculation formulas
has been developed to better estimate IOL power in these
patients, but most are wanting, and hyperopia remains a
frequent postoperative outcome. A dramatic method to
overcome refractive imprecision was recently reported by
Mackool and associates 13 in which post-LASIK patients
undergoing cataract surgery underwent immediate postoperative
aphakic refraction and then, one half-hour later,
were returned to the operating room for IOL implantation.
An alternative to the difficulties inherent in predicting
IOL power is use of a light adjustable lens. 14–18 The light
adjustable lens contains photosensitive silicone molecules
that enable postoperative, noninvasive adjustment of refractive
power using ultraviolet (UV) light. The light
adjustable IOL formulation consists of four basic components:
1) silicone matrix polymer, 2) photoreactive macromer,
3) photoinitiator, and 4) UV absorber. The light
adjustable IOL formulation has been described 14 previously
and is based upon the principles of photochemistry
and diffusion. The application of the appropriate wavelength
of light through a defined spatial irradiance profile
onto the light adjustable lens polymerizes macromer in the
exposed region producing a change in shape and associated
predictable power change. By controlling the irradiation
dose (ie, beam intensity and duration) and spatial irradiance
profile, the refractive power of the light adjustable
lens is modified to add or subtract spherical power, eliminate
astigmatic error, and correct higher-order aberrations
(HOAs). For example, to correct hyperopia, irradiation is
preferentially applied to the center of the lens. This causes
photopolymerization and subsequent diffusion of unpolymerized
macromer into the irradiated zone. Subsequent
swelling of the irradiated zone increases lens power to
correct hyperopia. To control the amount of hyperopia
corrected, the treatment duration is varied. One day after
light adjustable lens adjustment, the entire lens is irradiated
to polymerize the remaining photosensitive macromer
and prevent additional change in lens power. This second
irradiation procedure is referred to as “lock-in.”
To determine whether residual hyperopia could be
corrected postoperatively using the light adjustable lens
technology, we performed a clinical study in patients
undergoing cataract surgery with light adjustable IOL
implantation. Based on preoperative biometry, light adjustable
lenses were implanted that would purposely result
in hyperopic refractive errors up to 2.0 diopter (D). In
© 2009 BY ELSEVIER INC. ALL RIGHTS RESERVED.
392 0002-9394/09/$36.00
doi:10.1016/j.ajo.2008.08.039

FIGURE 1. Digital light delivery (DLD) device used to treat
patients with light adjustable intraocular lens (IOL) technology.
this fashion, we were able to adjust lens power and test
whether a “hyperopic surprise” could be corrected in the
postoperative period.
METHODS
A PROSPECTIVE, NONRANDOMIZED, SINGLE-CENTER CLINIcal
study was conducted at Codet Vision Institute, Tijuana,
Mexico. Subjects who required cataract extraction
and IOL implantation and volunteered for this study were
screened for eligibility. Subjects with significant anterior
segment pathology, uncontrolled glaucoma, previous ocular
surgery, macular deceases, current use of Flomax, or
7.0 mm dilated pupil diameter were excluded. Fourteen
patients (one eye per patient) were enrolled, 10 females
and four males.
Preoperative biometry was performed using an immersion
biometry unit (Axis II Ophthalmic Echograph; Quantel
Medical, Bozeman, Montana, USA), and the light
adjustable IOL power was selected to result in a postoperative
refractive error of up to 2.0 D of hyperopia. The
light adjustable IOL is a foldable posterior chamber, UV
absorbing, three-piece photoreactive silicone lens with
blue polymethylmethacrylate modified-C haptics, a 6.0
TABLE 1. Preoperative Refraction and Axial Length, and
Implanted Light Adjustable Intraocular Lens Power for
Patients With Light Adjustable Intraocular Lens
Technology
Eye
Preoperative
Sphere Cylinder Axial Length (mm)
Implanted
Power (D)
1 2.25 1.25 15 22.76 18.0
2 ND a ND a 23.16 20.0
3 0.75 0.75 90 23.43 20.0
4 4.00 1.50 99 22.04 23.5
5 2.75 0.75 80 22.59 21.5
6 2.50 0.00 0 22.63 23.5
7 1.50 0.00 0 22.31 21.5
8 5.00 0.75 100 22.55 23.0
9 3.00 0.75 75 22.85 22.0
10 3.00 0.75 75 22.90 23.0
11 2.00 0.00 0 22.56 22.5
12 3.25 2.00 90 23.58 20.0
13 2.75 0.75 80 22.88 20.5
14 1.75 0.00 0 22.79 22.5
D diopters; ND not determined.
a
No refraction can be measured attributable to dense
cataract.
TABLE 2. Distribution of Refractive Adjustments
Attempted for 14 Patients With Light Adjustable
Intraocular Lens Technology
Attempted Sphere n a /N b
0.25 to 0.5 D 3/14 21.4%
0.75 to 1.0 D 6/14 42.9%
1.25 to 1.5 D 4/14 28.6%
1.75 to 2.0 D 1/14 7.1%
D diopters.
a
Number of eyes at each attempted sphere.
b
Total eyes enrolled.
mm biconvex optic with squared posterior edge, and an
overall length of 13.0 mm.
All patients underwent phacoemulsification using a
topical anesthetic, clear corneal incision (3.0 to 3.5
mm) and anterior capsulotomy (5.5 mm). The light
adjustable IOL of the appropriate power was implanted
in the capsular bag using the Nichamin II Foldable Lens
Insertion Forceps (Rhein Medical Inc, Tampa, Florida,
USA). The operative eye was patched following surgery.
The patch was removed the following day, and patients
were instructed to wear Calhoun Vision-supplied UVblocking
photochromic spectacles (7EYE, Pleasanton,
California, USA) at all times when indoors and outdoors
after surgery until the adjustment and lock-in
procedures were completed.
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TABLE 3. Accountability of All Patients Enrolled With Light Adjustable Intraocular Lens Technology as a Function of
Postoperative Time
The light adjustable IOL was adjusted and locked in
using a digital light device engineered by Carl Zeiss
Meditec (Jena, Germany). 15,16 The digital light device
uses a mercury (Hg) arc lamp fitted with a narrow bandpass
interference filter producing a beam at 365 nm ( 4nm
full width half maximum). The digital light device generates
and projects a spatial irradiance pattern onto the light
adjustable IOL using a digital mirror device. The digital
mirror device is a pixelated, micromechanical spatial light
modulator formed monolithically on a silicon substrate.
The digital mirror device chip enables customization of the
irradiation profile to correct not only spherical and astigmatic
errors but also HOAs. The surgeon centers and
focuses the treatment beam on the light adjustable lens
using an alignment reticle while patient alignment is
achieved using a fixation target, parcentral to the delivery
beam. The digital light device is shown in Figure 1.
At one to two weeks postimplantation, best-corrected
and uncorrected visual acuity (VA) and residual hyperopic
refractive error were measured. VA assessment and manifest
refraction were performed by an optometrist who was
masked to the patient’s targeted refractive outcome and
light adjustable IOL power. The digital light device was
then used to adjust the light adjustable IOL power to
correct the hyperopic error. Refractive power adjustments
are defined at the spectacle plane. A second irradiation
treatment was given a minimum of 20 hours after adjustment
to lock-in the lens. The following study endpoints
were evaluated:
1. Attempted vs achieved lens power change (manifest
refraction).
2. VA (best-corrected and uncorrected distance VA).
3. Stability of adjusted lens power (manifest refraction).
4. Complications and adverse events.
RESULTS
A TOTAL OF 14 EYES WERE TREATED FOR REFRACTIVE ADjustments
in the range of 0.25 to 2.0 D and were
followed for one to six months postoperatively. Of the 14
patients, 10 were female and four were male. The average
One Month Three Months Six Months
Available for analysis n/N (%) 14/14 100.0% 14/14 100.0% 9/14 64.3%
Discontinued n/N (%) 0/14 0.0% 0/14 0.0% 0/14 0.0%
Missed visit n/N (%) 0/14 0.0% 0/14 0.0% 0/14 0.0%
Not yet eligible for the interval n/N (%) 0/14 0.0% 0/14 0.0% 5/14 35.7%
Lost to follow-up n/N (%) 0/14 0.0% 0/14 0.0% 0/14 0.0%
% Accountability
Availability for Analysis
(Enrolled Discounted Notyeteligible)
14/14 100% 14/14 100% 9/9 100%
FIGURE 2. Scattergram of target vs achieved hyperopic corrections
in patients with light adjustable IOL technology. The
solid line represents achieved refractive adjustments in diopters
(D) equal to the targeted power. Of 14 eyes adjusted, 13 (93%)
achieved 0.25 D of the targeted refractive adjustment in the
range of 0.25 to 2.0 D. The remaining one eye was within
0.50 D of the targeted refraction.
age of the study participants was 68 7 years. The power
of implanted light adjustable IOL as well as preoperative
refractive errors and axial length are presented in Table 1.
The distribution of refractive adjustments attempted can
be found in Table 2. All eyes were accounted for at the
one, three, and six month postoperative visits in Table 3.
There were no missed visits or any patients lost to
follow-up during the study period. An additional 14
patients were implanted with the light adjustable lens and
treated for refractive adjustments in the range of 2.0Dto
plano; these will be detailed in a separate report.
● TARGET VS ACHIEVED HYPEROPIC CORRECTIONS:
The accuracy of the achieved sphere to the targeted
refractive adjustment is demonstrated in the scattergram
presented in Figure 2 and data in Table 4. Thirteen of the
14 eyes (92.9%) treated were within 0.25 D of the target
refraction at one day post lock-in follow up visit with
100% of the eyes achieving 0.50 D of the targeted
refractive adjustment at one day post lock-in, three and six
months postoperative visits. Similar results were demonstrated
in the analysis of accuracy of the achieved manifest
394 AMERICAN JOURNAL OF OPHTHALMOLOGY
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TABLE 4. Accuracy of Sphere to Target – Hyperopic Corrections in Patients With Light
Adjustable Intraocular Lens Technology
Sphere
One Day Post Lock-In
refraction spherical equivalent presented in Table 5 demonstrating
no significant change was induced on cylinder.
● STABILITY OF REFRACTIVE ADJUSTMENT: One hundred
percent (14/14) of the eyes were stable within 0.25
D with 13 eyes showing no change at one to six months
follow-up visits as compared with refraction at one day
after lock-in treatment (Table 6). The mean rate of change
was 0.006 D per month, which is six times more stable
than that of refractive procedures. 19
● STABILITY OF UNCORRECTED VISUAL ACUITY: All
eyes demonstrated stability of uncorrected visual acuity
(UCVA) after lock-in. The bar graph of UCVA before
and after refractive adjustments is shown in Figure 3. The
data demonstrated significant improvement in UCVA for
64% of the 14 eyes and the UCVA is stable for a follow-up
period up to six months. Seventy-one percent (10/14) of
eyes achieved UCVA of 20/25 or better. All eyes were
20/30 or better. The four eyes that did not achieve UCVA
Three Months
Postoperative
Six Months
Postoperative
n/N % n/N % n/N %
% within 0.25 D of attempted 13/14 92.9% 13/14 92.9% 8/9 88.9%
% within 0.50 D of attempted 14/14 100.0% 14/14 100.0% 9/9 100.0%
% within 1.0 D of attempted 14/14 100.0% 14/14 100.0% 9/9 100.0%
D diopters.
TABLE 5. Accuracy of Manifest Refraction Spherical Equivalent to Target – Hyperopic
Corrections in Patients With Light Adjustable Intraocular Lens Technology
MRSE
One Day Post Lock-In
Three Months
Postoperative
Six Months
Postoperative
n/N % n/N % n/N %
% within 0.25 D of attempted 13/14 92.9% 13/14 92.9% 8/9 88.9%
% within 0.50 D of attempted 14/14 100.0% 14/14 100.0% 9/9 100.0%
% within 1.0 D of attempted 14/14 100.0% 14/14 100.0% 9/9 100.0%
D diopter; MRSE manifest refraction spherical equivalent.
TABLE 6. Stability of Refractive Adjustment in Patients
With Light Adjustable Intraocular Lens Technology
Change of Refraction (D) Number of Eyes Total 14 Follow-up Time (mos)
0 13 1–6
0.25 1 1–3
D diopters; mos months.
of 20/25 or better had residual astigmatism that was not
treated.
● STABILITY OF BEST-CORRECTED VISUAL ACUITY: BCVA
before and after refractive adjustments is displayed in
Figure 4. All 14 eyes were stable and able to maintain
their preadjustment BCVA following refractive adjustment
and lock-in treatments with follow-up time up to
six months.
● COMPLICATIONS: Any adverse events or complications
were recorded. In addition to typical adverse events associated
with IOLs, we looked carefully for evidence of
uveitis, UV keratopathy, elevated intraocular pressure,
posterior capsular opacity, glare, and halos. There were no
adverse events or complications reported.
DISCUSSION
HYPEROPIC REFRACTIVE ERROR AFTER CATARACT SURgery
is particularly undesirable since affected patients have
no clear uncorrected far point. Residual hyperopia is
particularly common after corneal refractive procedures
where preoperative keratometry measurements are unreliable.
Despite a wide array of empirical formulas, IOL power
remains difficult to predict in patients who develop cataracts
after refractive surgery. Herein, we demonstrate
feasibility of correcting residual hyperopic error after cataract
surgery using the light adjustable lens technology.
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FIGURE 3. Bar graph of uncorrected visual acuity (UCVA) before and after hyperopic corrections in patients with light
adjustable IOL technology. UCVA was expressed by converting the Snellen fraction to a numerical number, 20/20 1.0,
20/25 0.8, 20/30 0.67, 20/40 0.5, 20/50 0.4, 20/60 0.33, 20/80 0.25, and 20/100 0.2. Significant
improvement in UCVA was observed in 64% of eyes. Of 14 eyes, 10 eyes (71%) achieved an UCVA of 20/25 or better. All
eyes were 20/30 or better and stable for a follow-up period up to six months.
FIGURE 4. Bar graph of best-corrected visual acuity (BCVA) before and after hyperopic corrections in patients with light
adjustable IOL technology. BCVA was expressed by converting the Snellen fraction to a numerical number, 20/20 1.0,
20/25 0.8, 20/30 0.67, 20/40 0.5, 20/50 0.4, 20/60 0.33, 20/80 0.25, and 20/100 0.2. All eyes were stable
and able to maintain their preadjustment BCVA.
Correction of hyperopia between 0.25 to 2.0 D was
achieved with 90% of patients corrected to within 0.25
D of the intended refraction. While this was a feasibility
study and adjustments were performed in patients who had
not had previous refractive surgery, it is likely that correction
of hyperopia could be performed in a similar fashion in
these patients as well.
Uncorrected VA improved in 64% of patients while
BCVAs was maintained after lock-in in all patients. The
uncorrected and best-corrected VAs were stable for all
patients up to six months follow-up visit. One hundred
percent of the eyes were stable within 0.25 D with 13
eyes showing no change at one to six months follow-up
visits.
396 AMERICAN JOURNAL OF OPHTHALMOLOGY
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An important aspect of the light adjustable lens is the
need to wear UV protective spectacles until lock-in is
performed. This is because the photoreactive silicone
macromer undergoes photopolymerization when exposed
to UV light. The light adjustable lens has approximately
one hour of built in UV protection in the absence of
sunglasses (Chang SH, unpublished data, 2006), but after
that, there is a risk for photopolymerization and optical
changes. Therefore, patients are instructed to wear the UV
blocking sunglasses until lock-in is completed. After lockin,
no UV protection is necessary.
While this study demonstrates precise adjustment of
hyperopia between 0.25 to 2.0 D, the eye would
require a second adjustment to correct more than 2.0 D
before lock-in. Chemical analysis of light adjustable lenses
reveals that photoreactive macromer is available to undergo
multiple photo-polymerization leading to additional
refractive change as long as the lens is not locked-in. In
vitro studies have achieved a 3.5 D power change with
secondary adjustments of light adjustable lenses.
The light adjustable lens and digital light device provide
surgeons a means to fine tune refractive power in the
postoperative period. In this small pilot series of patients
treated for residual hyperopia, adjustments were precise
and stable for up to six months follow-up. This technology
may provide greater confidence in final refractive outcome
as increasing numbers of corneal refractive surgery patients
age and develop cataracts.
THIS STUDY WAS SUPPORTED BY SMALL BUSINESS INNOVATIVE RESEARCH GRANT NO. EY12181-02. DRS SANDSTEDT, CHANG,
Rhee, and Tsuchiyama are Calhoun Vision employees. Dr Chayet is a clinical investigator for Calhoun Vision. Dr Schwartz is the founder of Calhoun
Vision with financial interest. Involved in design of study (A.C., C.S., S.C., B.T., P.R., D.S.); conduct of study (A.C.); collection, management, analysis
and interpretation of the data (A.C., C.S., S.C., P.R., B.T., D.S.); preparation of the manuscript (A.C., S.C., D.S.); and review or approval of the
manuscript (A.C., C.S., S.C., B.T., P.R., D.S.). The clinical trial was approved and registered with Ministry of Health, the Secretaria de Salud, No.
204/004209, in Mexico City, Mexico. The studies were approved by Codet Vision Institute Institutional Review Board, Comite De Investigacion y Etica,
in Tijuan, Mexico. The study was performed in accordance with the Declaration of Helsinki and all patients gave written informed consent for research.
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Biosketch
Artura Chayet, MD, is the Director of Codet Vision Institute, in Tijuana, Mexico and a Past-President of the Mexican
Society of Refractive Surgery. He received his degree in Cornea and Refractive Surgery at the University of California,
San Diego, California. Dr Chayet has become one of the world’s leading refractive surgeons. He has been recognized
worldwide for contributing to the development of instruments, techniques, and software used in refractive surgery today.
397.e1 AMERICAN JOURNAL OF OPHTHALMOLOGY
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